Dicarboxylic acids (diacids) are important compounds that are used in the manufacture of commercial polymers (e.g. polyesters, polyurethanes). For example, see FIG. 1. The diacid adipic acid [1] is used mainly as a monomer in the production of nylon [2], a polyamide generated through the reaction of [1] with hexane-1,6-diamine. Polyesters (for use in fabrics and plastics of many compositions) are formed through the polymerization of terphthalic acid [3] and a dialcohol (diol) such as ethylene glycol (to make polyethylene terephalate [4]), propane diol (poly(1,3-propanediol terephthalate) [5]) or butanediol (poly(1,4-butanediolphthalate) [6]. Adipic acid is also used in the synthesis of various polyesters.
The large scale worldwide use of nylons and polyesters requires the production of approximately 8 billion metric tons of [1] and 15 billion metric tons of [3] annually. These diacids are themselves synthesized from starting materials extracted from petroleum. One means of reducing the large dependence on oil for the commercial production of polymers is to generate the diacids by a fermentation process involving the use of polyketide synthases.